Conductive particle interconnect switch

ABSTRACT

Provided is an apparatus comprising a conductive particle interconnect (CPI) and an electroactive polymer (EAP) structure. The CPI includes an elastomeric carrier and a plurality of conductive particles dispersed therein. The EAP structure is disposed around at least a portion of the CPI. The EAP structure is configured to move between a first position and a second position in response to an electrical field. The CPI is configured to exhibit a first electrical resistance when the EAP structure is in the first position and a second, different electrical resistance when the EAP structure is in the second position.

BACKGROUND

The present disclosure relates generally to the field of electricalswitches, and more particularly to switches having electroactivepolymers and conductive particle interconnects.

Switches are often used to control the flow of electricity betweenvarious components in a circuit. Switches typically include contactsthat form electrical connections with one or more components. Amechanical switch can be thought of as having a variable resistance thatchanges from a large or effectively infinite resistance (e.g., an open,whereby electricity does not freely flow through the switch) when theswitch contacts are not touching to a low or near zero resistance (e.g.,a short, whereby electricity freely flows) when the switch contacts aretouching. Other switching structures, such as transistors, also exhibita variable resistance.

SUMMARY

Embodiments of the present disclosure include an apparatus. Theapparatus comprises a conductive particle interconnect (CPI) and anelectroactive polymer (EAP) structure. The CPI includes an elastomericcarrier and a plurality of conductive particles dispersed therein. TheEAP structure is disposed around at least a portion of the CPI. The EAPstructure is configured to move between a first position and a secondposition in response to an electrical field. The CPI is configured toexhibit a first electrical resistance when the EAP structure is in thefirst position and a second, different electrical resistance when theEAP structure is in the second position.

Additional embodiments of the present disclosure include a method,system, and computer program product. The method comprises determining atarget state of a CPI. The method further comprises generating an inputsignal based on the target state. The input signal is transmitted to avoltage source to cause an EAP disposed around the CPI to apply a forceon the CPI. The applied force causes the CPI to transition to the targetstate.

The above summary is not intended to describe each illustratedembodiment or every implementation of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings included in the present disclosure are incorporated into,and form part of, the specification. They illustrate embodiments of thepresent disclosure and, along with the description, serve to explain theprinciples of the disclosure. The drawings are only illustrative oftypical embodiments and do not limit the disclosure.

FIGS. 1A and 1B are diagrams illustrating two states of a first exampleswitch that includes an electroactive polymer (EAP) and a conductiveparticle interconnect (CPI), in accordance with embodiments of thepresent disclosure.

FIGS. 2A and 2B are diagrams illustrating two states of a second exampleswitch that includes an EAP and a CPI, in accordance with embodiments ofthe present disclosure.

FIGS. 3A and 3B are sectional view diagrams illustrating two states of athird example switch that includes an EAP and a CPI, in accordance withembodiments of the present disclosure.

FIG. 4 is a block diagram of a system that includes an EAP-actuated CPIswitch coupled to other circuitry for controlling and using the switch,in accordance with embodiments of the present disclosure.

FIG. 5 illustrates a flowchart of an example method for using anEAP-actuated CPI switch, in accordance with embodiments of the presentdisclosure.

FIG. 6 illustrates a high-level block diagram of an example computersystem that may be used in implementing one or more of the methods,tools, and modules, and any related functions, described herein, inaccordance with embodiments of the present disclosure.

While the embodiments described herein are amenable to variousmodifications and alternative forms, specifics thereof have been shownby way of example in the drawings and will be described in detail. Itshould be understood, however, that the particular embodiments describedare not to be taken in a limiting sense. On the contrary, the intentionis to cover all modifications, equivalents, and alternatives fallingwithin the spirit and scope of the invention.

DETAILED DESCRIPTION

Aspects of the present disclosure relate generally to the field ofelectrical switches, and in particular to switches having electroactivepolymers and conductive particle interconnects. While the presentdisclosure is not necessarily limited to such applications, variousaspects of the disclosure may be appreciated through a discussion ofvarious examples using this context.

The present disclosure relates to switches that include electroactivepolymer (EAP) structures and a conducting particle interconnect (CPI). ACPI may be formed by doping a compliant elastomeric carrier (e.g., apolymer) with conductive particles. When the conductive particlesinclude metal particles, the CPI may be referred to as a metalizedparticle interconnect (MPI). Metal particles (or flakes) used in MPIsinclude, but are not limited to, copper, silver, gold, and/or nickel, aswell as various alloys and plated materials.

The resistance of a CPI can be modified through compression/expansion ofthe CPI (e.g., of the CPI's polymer base). For example, as a CPI iscompressed, the average gap between conductive particles is decreaseddue to the same number of particles being disposed within a smallervolume. This increases the number of conductive particles that are incontact with each other, thereby reducing the resistance of the CPI andallowing electric current to flow more easily within, on, or through theCPI. Conversely, when compression decreases, the volume of the CPIincreases, the conductive particles move farther apart, the number ofconductive particles that are in contact with each other decreases, andthe resistance of the CPI increases.

An electro-active polymer (EAP) is a polymer or a set of polymers (e.g.,a co-polymer system or a laminate of polymers) that exhibits a change ofsize or shape when subjected to an electric field. In an EAP structure,an EAP is positioned between two electrodes such that the electrodes canapply the electric field to the EAP. Examples of EAPs includeferroelectric polymers (e.g., a polyvinylidene fluoride),electrostrictive graft polymers, and ionic EAPs (e.g., intrinsicallyconducting polymers, such as polyacetylene and polyphenylene vinylene)or ionic polymer-metal composites, which are similar to dielectric EAPsexcept that the polymer itself is conductive. Some EAPs retain theirshape/size after removal of the electric field, while others revert backto their default shape/size when the electric field is removed.Furthermore, the magnitude of the size/shape change of an EAP may dependon the strength of the electric field.

In some embodiments, a CPI is combined with an EAP structure (ormultiple EAP structures) to form a polymer-based switch. The switch maybe used, for example, to toggle downstream circuits between active(e.g., “on”) and inactive (e.g., “off”) states, or to toggle inputs todownstream circuits (e.g., one or more inputs to an AND gate) between a1 and a 0. The EAP structure(s) act to increase or decrease thecompression of the CPI, thereby changing the resistance of the CPI. Inother words, the CPI acts as a variable resistance based on the amountof force applied to the CPI by the EAP structure(s). Using theseproperties, the CPI can be used as a switch. For example, the switch is“closed” when the CPI has a first resistance (e.g., a low resistance),and the switch is “open” when the CPI has a second resistance (e.g., ahigh resistance). The switch may also exhibit a variety of resistancevalues between a fully open resistance value (e.g., a maximum resistancevalue of the CPI) and a fully closed resistance value (e.g., a minimumresistance value of the CPI). Thus, the switch can have multiplepositions including fully open, fully closed, and one or moreintermediate positions. This may be achieved by varying the strength ofthe electric field that the EAP structure(s) are subjected to.

In some embodiments, the switch may be actuated (e.g., opened or closed)by application of a voltage across the EAP structure(s). The appliedvoltage generates an electric field which causes the EAP to contract,expand, and/or change shape. The EAP structure(s) may be integrated withthe CPI such that movement of the EAP, relative to the CPI, due to theelectric field changes the force applied to the CPI. For example, if theswitch is closed, the switch may be opened by movement of the EAP thatreduces the compressive force applied to the CPI, which increases theresistance of the CPI. Similarly, the switch may be toggled from theopen state to the closed state by application of a voltage that causesthe EAP to increase the compressive force applied to the CPI, whichreduces the resistance of the CPI. The switch can be configured as anormally open switch, which may also be referred to as a fail openswitch (e.g., a switch that is open unless a voltage is applied to theEAP to close it), as a normally closed switch, which may also bereferred to as a fail closed switch (e.g., a switch that is closedunless a voltage is applied to the EAP to open it), or a switch that isin an intermediate state (e.g., not fully open or closed) when novoltage is applied to the EAP.

In some embodiments, a silicone dielectric elastomer is filled with aconductive metal particle below the percolation limit. In other words,the conductive metal particles are directly embedded in a polymer (e.g.,a polymer matrix) that includes, or is made out of, the EAP (e.g., thesilicone dielectric elastomer). As used herein, the percolation limit ofthe CPI includes an amount or concentration of conductive particlesabove which the CPI's resistance drops significantly (e.g., measurably,such that electricity begins flowing through the CPI). By keeping theamount of conductive metal particles below the percolation limit, theCPI starts in a fail-open state (i.e., acts as an open switch when novoltage is applied to the EAP). Once the actuation voltage is applied tothe EAP(s), the elastomer is placed under compressive strain, the metalparticles provide a continuous conduction path, and the percolationlimit is exceeded, resulting in a conducting elastomer. Note thatdielectric EAPs require no power to keep the actuator at a givenposition. An example EAP-actuated CPI switch according to theseembodiments is illustrated in FIGS. 1A and 1B.

In some embodiments, such as those applications that undergo thermalcycling that could experience an electrical glitch on the cooling cycledue to contraction of the CPI when cooled, an EAP-actuated CPI may befabricated with the filler loading exceeding the percolation limit. Thatis, the EAP-actuated CPI may have sufficient conductive filler (e.g.,particles) to be conductive even prior to the application of any forcefrom the EAP. Using temperature sensing circuitry already present in thesystem, a DC bias voltage may be applied to the EAP-actuated CPI onlytoward the low end of the cooling cycle in order to provide positivenormal force on the contacts (e.g., to counteract the constrictioncaused by the cooler temperature).

In some embodiments, a separate EAP is used to constrict the CPI, whichmay include a normal (i.e., not electroactive) polymer matrix in whichconductive particles are embedded. In these embodiments, a differentclass of EAP other than a dielectric elastomer may be utilized. Whendielectric elastomers are not used, the EAP may require continuousapplication of the actuation voltage in order to retain its compressedform. An example EAP-actuated CPI switch where a separate EAP is used toconstrict a CPI is illustrated in FIGS. 2A-3B.

Embodiments of the present disclosure include an EAP-actuated CPI havingan EAP elastomeric carrier. The EAP-actuated CPI comprises a CPI havingan elastomeric carrier and a plurality of conductive particles dispersedtherein. The elastomeric carrier includes an EAP configured to movebetween a first position and a second position in response to anelectrical field. The CPI is configured to exhibit a first electricalresistance when the EAP is in the first position and a second electricalresistance when the EAP is in the second position. The apparatus furthercomprises one or more electrodes electrically coupled to the CPI. Theelectrodes are configured to generate the electrical field within theCPI. The apparatus further comprises one or more insulators coupled tothe CPI. The one or more insulators are configured to constrainexpansion of the CPI in at least one direction.

Additional embodiments of the present disclosure include a method,system, and computer program product for controlling an EAP-actuated CPIhaving an EAP elastomeric carrier. The method comprises determining atarget state of a CPI that includes an elastomeric carrier having an EAPand a plurality of conductive particles. The EAP is configured to movebetween a first position and a second position in response toapplication of an electrical field. The second position is associatedwith the target state. The method further comprises generating an inputsignal based on the target state. The input signal is transmitted to avoltage source. Transmission of the input signal to the voltage sourcecauses the voltage source to apply the electrical field to the EAP tomove the EAP to the second position.

Embodiments of the present disclosure include an EAP-actuated CPI havingan EAP structure that is external to the CPI. The EAP-actuated CPIcomprises a CPI and an EAP structure. The CPI includes an elastomericcarrier and a plurality of conductive particles dispersed therein. TheEAP structure is disposed around at least a portion of the CPI. The EAPstructure is configured to move between a first position and a secondposition in response to an electrical field. The CPI is configured toexhibit a first electrical resistance when the EAP structure is in thefirst position and a second, different electrical resistance when theEAP structure is in the second position.

Additional embodiments of the present disclosure include a method,system, and computer program product for controlling an EAP-actuated CPIhaving an EAP structure that is external to the CPI. The methodcomprises determining a target state of a CPI. The method furthercomprises generating an input signal based on the target state. Theinput signal is transmitted to a voltage source to cause an EAP disposedaround the CPI to apply a force on the CPI. The applied force causes theCPI to transition to the target state.

Turning now to the figures, FIGS. 1A and 1B are diagrams illustratingtwo states of a first example switch 100 that includes an electroactivepolymer (EAP) and a conductive particle interconnect (CPI), inaccordance with embodiments of the present disclosure. The EAP-actuatedCPI switch 100 illustrated in FIGS. 1A and 1B includes a CPI having anelastomeric carrier comprising an EAP matrix 106 (e.g., a siliconedielectric elastomer matrix) in which conductive particles 108 (e.g.,conductive metal particles) are embedded. The EAP matrix 106 is incontact with a pair of electrodes 102 a, 102 b and an insulator material104 a, 104 b.

As shown in FIG. 1A, the EAP-actuated CPI switch 100 may initially startin an open state. In other words, the EAP-actuated CPI switch 100 may bea “fail-open” switch that does not allow current to flow between signalcontacts (not shown) when no electric field is applied to the EAP by theelectrodes 102 a, 102 b. The EAP-actuated CPI switch may be created byfilling an EAP matrix 106 with conductive particles 108 below thepercolation limit.

When an actuation voltage is applied to the EAP matrix 106 through theelectrodes 102 a, 102 b, the EAP matrix 106 is placed under acompressive strain and contracts along the directions indicated by thearrows 110, as shown in FIG. 1B. The contraction, which is aided by theinsulator(s) 104 a, 104 b, causes the density of conductive particles108 to increase, reducing the distance between conductive particles 108and increasing the number of conductive particles that are in physicalcontact with each other. This creates a conductive path through theEAP-actuated CPI switch 100, causing the EAP-actuated CPI switch 100 totransition to the closed state. In embodiments that use a dielectric EAPas the EAP matrix 106, the actuation voltage can be removed after theEAP-actuated CPI switch 100 changes state because dielectric EAPs retaintheir shape after removal of the electric field.

Use of this type of CPI may eliminate the electrical glitches that canoccur when a traditional CPI is subjected to thermal cycling. That is,when the system enters a cooling cycle, the interconnect may experienceintermittent electrical contact resulting in opens. Although the FIGS.1A and 1B depict the electrodes on the top and bottom of the CPI, oneskilled in the art will appreciate that many different electrodeconfigurations are possible. In order to prevent the electrical glitchesthat may occur upon cooling, the electrodes may be positioned on thesides of the CPI so that upon actuation, the sides are compressed and aresulting normal force (in the z-axis or thickness of the CPI) isapplied to the mating contacts. If the CPI is actuated at the low end ofthe operating temperature range, a positive normal force may be presentthroughout thermal cycling.

In some embodiments, the EAP-actuated CPI switch 100 may have more thantwo states. For example, application of a first voltage may result inthe EAP-actuated CPI switch 100 being in a first state with a firstelectrical resistance (e.g., an open state), application of a secondvoltage may result in the EAP-actuated CPI switch 100 being in a secondstate with a second electrical resistance (e.g., a closed state), andapplication of a third voltage that is between the first and secondvoltages causes the EAP-actuated CPI switch 100 to exhibit a thirdelectrical resistance that is between the first electrical resistanceand the second electrical resistance. Thus, the EAP-actuated CPI switch100 may have a continuous or discrete range of states between andincluding the first state of FIG. 1A and the second state of FIG. 1B.

Turning now to FIGS. 2A and 2B, depicted are diagrams illustrating twostates of a second example switch 200 that includes an EAP and a CPI, inaccordance with embodiments of the present disclosure. The EAP-actuatedCPI switch 200 illustrated in FIGS. 2A and 2B includes a CPI 202 (e.g.,a polymer in which conductive particles 208 (e.g., conductive metalparticles) are embedded). A discrete EAP structure 204 surrounds atleast part of the CPI 202. The EAP structure 204 may be electricallyconnected to a pair of electrodes (not shown) that are configured toapply an actuation voltage to the EAP structure 204.

As shown in FIG. 2A, the EAP-actuated CPI switch 200 may initially startin an open state when subjected to a first voltage V1 206 a. In otherwords, the EAP-actuated CPI switch may be a “fail-open” switch that doesnot allow current to flow between the signal contacts when V1 is appliedto the EAP. In this state, the EAP structure 204 may have a firstdiameter d1. The CPI 202 may be created by filling the elastomericcarrier (e.g., polymer) with conductive particles 208 below thepercolation limit.

When an actuation voltage V2 206 b is applied to the EAP structure 204by control circuitry (e.g., a processor, not shown), the EAP structure204 generates a compressive force F, as shown in FIG. 2B. Thecompressive force F causes the EAP structure 204 to constrict. Afterconstriction, the EAP structure 204 has a second diameter d2. The seconddiameter d2 is less than the first diameter d1. Accordingly, the CPI 202is likewise placed under compression and constricts. The constriction ofthe CPI 202 causes the density of conductive particles 208 to increasedue to the decreased volume occupied by the CPI, reducing the distancebetween conductive particles 208 and increasing the number of conductiveparticles that are in physical contact with each other. This creates aconductive path through the CPI 202, reducing the electrical resistanceof the CPI 202 (e.g., causing the EAP-actuated CPI switch 200 totransition to the closed state).

In some embodiments, the EAP structure 204 may include a dielectric EAP.In these embodiments, the actuation voltage can be removed after theEAP-actuated CPI switch 200 changes states because dielectric EAPsretain their shape after removal of the electric field. In order tochange the EAP-actuated CPI switch 200 to the original state (e.g.,transition the EAP back to its original shape), a different electricfield must be applied to the dielectric EAP. In other embodiments, theactuation voltage may be continuously applied to the EAP structure 204to keep the EAP structure 204 in the constricted state shown in FIG. 2B.

In some embodiments, the EAP-actuated CPI switch 200 may have more thantwo states. For example, application of a first voltage may result inthe EAP-actuated CPI switch 200 being in a first state with a firstelectrical resistance (e.g., an open state), application of a secondvoltage may result in the EAP-actuated CPI switch 200 being in a secondstate with a second electrical resistance (e.g., a closed state), andapplication of a third voltage that is between the first and secondvoltages causes the EAP-actuated CPI switch 200 to exhibit a thirdelectrical resistance that is between the first electrical resistanceand the second electrical resistance. Thus, the EAP-actuated CPI switch200 may have a continuous or discrete range of states between andincluding the first state of FIG. 2A and the second state of FIG. 2B.

Turning now to FIGS. 3A and 3B, depicted are sectional view diagramsillustrating a top view and a side view of a third example switch 300 intwo states, in accordance with embodiments of the present disclosure.The third switch 300 may be the same as, or substantially similar to,the second switch 200 illustrated in FIGS. 2A and 2B. The EAP-actuatedCPI switch 300 illustrated in FIGS. 3A and 3B includes a CPI 302. TheCPI may, for example, be made of a polymer in which conductive particles308 (e.g., conductive metal particles) are embedded. A discrete EAPstructure 304 surrounds at least part of the CPI 302. The EAP structure304 may be electrically connected to a pair of electrodes 310 a, 310 bthat are configured to apply an actuation voltage to the EAP structure304. Additionally, the EAP-actuated CPI switch 300 includes two signalcontacts 312 a, 312 b.

As shown in FIG. 3A, the EAP-actuated CPI switch 300 may initially startin an open state when subjected to a first voltage 306 a. In this state,the distance between conductive particles 308 may be sufficiently largeto prevent current from flowing though the EAP-actuated CPI switch 300(e.g., between signal contacts 312 a and 312 b). The CPI 302 may becreated by filling a polymer with conductive particles 308 below thepercolation limit. As shown in FIG. 3A, the EAP structure 304 is ahollow tube that surrounds the CPI 302.

When an actuation voltage 306 b is applied to the EAP structure 304 bycontrol circuitry (e.g., a processor, not shown), the EAP structure 304generates a compressive force F, as shown in FIG. 3B. The actuationvoltage 306 b may be applied to the EAP structure 304 using theelectrodes 310 a, 310 b. The compressive force F causes the EAPstructure 304 to constrict, squeezing the CPI 302. Accordingly, the CPI302, is likewise placed under compression and constricts. Theconstriction of the CPI 302 causes the density of conductive particles308 to increase, reducing the distance between conductive particles 308and increasing the number of conductive particles that are in physicalcontact with each other. This creates a conductive path through the CPI302, reducing the electrical resistance of the CPI 302 (e.g., causingthe EAP-actuated CPI switch 300 to transition to the closed state). Acurrent is then able to flow through the EAP-actuated CPI switch 300 andinto the signal contacts 312 a, 312 b.

In some embodiments, the constriction of the EAP structure 304 and theCPI 302 along one or two dimensions (as shown in FIG. 2B) causesexpansion of the CPI 302 in a third dimension. In other words, the CPI302 is squeezed by the EAP 304 that surrounds it, causing the CPI toexpand towards the signal contacts 312 a, 312 b. This expansion providesa positive normal force on the contacts 312 a, 312 b. Accordingly, thecontact forces between the CPI 302 and the signal contacts 312 a, 312 bis increased. This reduces the electrical resistance at the boundariesbetween the CPI 302 and the contacts 312 a, 312 (e.g., decreases thecontact resistance), thereby increasing the electrical conductivity ofthe CPI 302 at the interface between the CPI 302 and the signal contacts312 a, 312 b.

In some embodiments, the EAP-actuated CPI switch 300 may have more thantwo states. For example, application of a first voltage may result inthe EAP-actuated CPI switch 300 being in a first state with a firstelectrical resistance (e.g., an open state), application of a secondvoltage may result in the EAP-actuated CPI switch 300 being in a secondstate with a second electrical resistance (e.g., a closed state), andapplication of a third voltage that is between the first and secondvoltages causes the EAP-actuated CPI switch 300 to exhibit a thirdelectrical resistance that is between the first electrical resistanceand the second electrical resistance. Thus, the EAP-actuated CPI switch300 may have a continuous or discrete range of states between andincluding the first state of FIG. 3A and the second state of FIG. 3B.

In some embodiments, a circuit may be coupled to any of the abovedescribed switches 100, 200, 300 to generate an output signal based onthe electrical resistance of the CPI. For example, the circuit mayinclude a voltage source that applies a known or fixed voltage acrossconductive contacts that are coupled to the CPI. In this example, theoutput signal generated by the circuit may correspond to or indicatecurrent that flows through the CPI responsive to the voltage appliedacross the conductive contacts. Since the resistance of the CPI changesbased on the position of the EAP structure, the current of the outputsignal corresponds to or indicates the position of the EAP structure.

For example, when the EAP structure 304 is in the first position, asillustrated in FIG. 3A, the CPI 302 has a first electrical resistance(R1) resulting in the circuit generating a first output signal (S1)(e.g., a first current). Further, when the EAP structure 304 is in thesecond position, as illustrated in FIG. 3B, the CPI 302 has a secondelectrical resistance (R2) resulting in the circuit generating a secondoutput signal (S2) (e.g., a second current). Because the secondelectrical resistance (R2) is less than the first electrical resistance(R1) and the voltage applied across the conductive contacts 312 a, 312 bis fixed or known, the second output signal (S2) has a higher currentthan the first output signal (S1).

Thus, the EAP structure 304 and CPI 302 can be arranged to form a switch300 or variable resistance device in order to generate an output signal.EAP structures respond quickly to applied electrical fields. Thus, ifthe control signal is modulated (e.g., time varying), the output signalvaries based on the modulation of the control signal.

Each of the switches described above (e.g., switches 100, 200 and 300)is illustrated as including a single CPI coupled to, or having as itspolymer matrix, at least one EAP structure. However, in someimplementations, a switch may include more than one CPI. In suchimplementations, each CPI may exhibit a corresponding electricalcharacteristic (e.g., electrical resistance) based on a position of oneor more EAP structures.

While each of the above switches (e.g., switches 100, 200, and 300) useEAPs that constrict when subjected to an electric field, in someembodiments, an EAP that expands when subjected to an electric field maybe used as the EAP matrix (e.g., in FIGS. 1A and 1B) and/or as thediscrete EAP structure (e.g., in FIGS. 2A and 2B). In these embodiments,the EAP-actuated CPI switch may start in the closed state. When theactuation voltage is applied, the EAP matrix may expand, causing theEAP-actuated CPI switch to transition to the open state by relaxing oreliminating the compressive strain on the CPI.

Turning now to FIG. 4, depicted is a block diagram of a system 400 thatincludes a switch coupled to other circuitry for controlling and usingthe switch, in accordance with embodiments of the present disclosure.The switch of FIG. 4 is an EAP-actuated switch 406 that includes atleast one CPI and at least one EAP. For example, the EAP-actuated switch406 may correspond to, or include, the switch 100 of FIGS. 1A and 1B,the switch 200 of FIGS. 2A and 2B, or the switch 300 of FIGS. 3A and 3B.

The system 400 also includes control circuitry 402 that is coupled to afirst voltage source 404A via an input line 410. In some embodiments,the control circuitry 402 is dedicated hardware for controlling theEAP-actuated CPI switch 406. In some embodiments, the control circuitry402 includes a processor. The control circuitry 402 may also, or in thealternative, include a sensor, one or more logic gates, anapplication-specific integrated circuit (ASIC), a field programmablegate array (FPGA), or any other circuitry capable of generating an inputsignal 411 and providing the input signal 411 to the first voltagesource 404A.

The first voltage source 404A is electrically connected to theEAP-actuated switch 406 via one or more control lines 412. The firstvoltage source 404A may provide a control signal 413 (or more than onecontrol signal) to the EAP-actuated switch 406 via the control line 412(or more than one control line) in order to cause the EAP-actuatedswitch 406 to change states. For example, when the EAP-actuated switch406 corresponds to the switch 200, the first voltage source 404A may beconfigured to provide a single control signal 413 to the EAP structure204 to toggle the EAP-actuated switch 406 between a first and secondstate (e.g., the open and closed states).

In some embodiments, such as those with multiple EAP structures, thefirst voltage source 404A may be configured to provide multiple controlsignals 413. For example, the first voltage source 404A may provide afirst control signal to a first EAP structure, and it may also provide asecond control signal to a second EAP structure. In other embodiments,the first voltage source 404A may be configured to provide the controlsignal to the first EAP structure, and another voltage source (e.g., thesecond voltage source 404B and/or another voltage source that is notshown) may independently provide the control signal to the second EAPstructure.

In some embodiments, the system 400 includes a second voltage source404B. The second voltage source 404B may be electrically connected tothe EAP-actuated switch 406. While the first voltage source 404A may beused to generate an electric field across/within the EAP structures, thesecond voltage source 404B may apply a second voltage (e.g., a constantvoltage) to the CPI portion of the EAP-actuated switch 406. This secondvoltage may drive the current through the EAP-actuated switch 406 and todownstream circuits when the EAP-actuated switch 406 is closed. In otherwords, the first voltage source 404A may control the state of theEAP-actuated switch 406 by applying an electric field to the EAPmaterials, whereas the second voltage source 404B may drive the currentthat flows through the EAP-actuated switch 406 and to other circuits.

The EAP-actuated switch 406 exhibits an electrical characteristicresponsive to the control signal(s) 413. For example, the EAP-actuatedswitch 406 may exhibit a particular electrical resistance responsive tothe control signal(s). The electrical characteristic may be detected byread circuitry 408. The read circuitry 408 may be coupled to theEAP-actuated switch 406 via one or more read lines 414. The readcircuitry 408 may receive a read signal 415 (or read signals) from theEAP-actuated switch 406 and generate an output signal 417 indicative ofthe electrical characteristic of the EAP-actuated switch 406 based onthe read signal(s) 415. For example, the read circuitry 408 (or thesecond voltage source 404B) may apply a known or fixed voltage signal toa CPI of the EAP-actuated switch 406. In this example, the output signal417 may include a current that flows through the EAP-actuated switch 406based on the known or fixed voltage and the resistance of the CPI. Theoutput signal 417 may be provided, via an output line 416, to one ormore other circuit components (not shown).

In some embodiments, a monitoring line 418 may connect the readcircuitry 408 to the control circuitry 402. A monitoring signal 419 maybe transmitted to the control circuitry 402 on the monitoring line 418.Using the monitoring signal 419, the control circuitry can determinewhether the EAP-actuated switch 406 is in the proper state. For example,the monitoring signal 419 may show that no current is flowing betweenthe EAP-actuated switch 406 and the read circuitry 408, indicating thatthe EAP-actuated switch 406 is in the open state. If the controlcircuitry 402 established that the EAP-actuated switch 406 should be ina different state (e.g., a closed state), the EAP-actuated switch 406may, in response to receiving the monitoring signal 419, transmit a newinput signal to the first voltage source 404A to increase (or decrease)the voltage applied by the first voltage source 404A to the EAP-actuatedswitch 406, thereby changing the electrical characteristics of theEAP-actuated switch 406.

In some embodiments, the system 400 may act as a variable resistor.Accordingly, the control circuitry 402 may determine, from themonitoring signal 419, the resistance of the EAP-actuated switch 406.The control circuitry 402 can then adjust, as necessary, the voltageapplied to the EAP-actuated switch 406 by the first voltage source 404Athe change the resistance of the EAP-actuated switch 406, and,therefore, of the system 400. This may be particularly useful when theysystem is subject to thermal cycling as the electrical characteristicsof the EAP-actuated switch 406 may change with temperature changes.

Turning now to FIG. 5, illustrated is a flowchart of an example method500 of using an EAP-actuated CPI switch, in accordance with embodimentsof the present disclosure. One or more operations of the method 500 maybe performed by control circuitry, and one or more other operations maybe performed by an EAP-actuated switch. The control circuitry mayinclude a processor configured to perform one or more of the operationsof the method 500, and/or specialized hardware (e.g., an ASIC). TheEAP-actuated CPI switch may be any CPI switch that is actuated by anEAP, such as the switch 100 of FIGS. 1A and 1B, the switch 200 of FIGS.2A and 2B, the switch 300 of FIGS. 3A and 3B, or the EAP-actuated CPIswitch 406 of FIG. 4. For example, the switch may include an EAPstructure that is configured to move between a first position and asecond position responsive to an electrical field associated with acontrol signal.

The method 500 may begin at operation 502, wherein the control circuitrycan determine the target state of an EAP-actuated CPI switch. The targetstate may be any of a fully open state, a fully closed state, or one ormore intermediate states between fully open and fully closed. In someembodiments, the target state may be associated with a target voltage,which may be determined at operation 504. The target voltage is avoltage that causes the switch to transition to, or be placed in, thetarget state.

At operation 506, the control circuitry may generate and send an inputsignal to a voltage source. The input signal may instruct and/or causethe voltage source to generate a control signal that applies the targetvoltage to the switch.

At operation 508, the switch receives the control signal. For example,the control signal may be a voltage applied to an EAP structure of theswitch, causing the EAP structure to move between a first position and asecond position. In other words, the control signal may cause the switchto transition to the target state.

At operation 510, the switch generates, responsive to the controlsignal, an output (e.g., a current) based on an electrical resistancecharacteristic of a CPI of the switch. The CPI includes an elastomericcarrier and conductive particles dispersed therein. The CPI isconfigured to exhibit a first electrical resistance when the EAPstructure is in the first position and to exhibit a second electricalresistance when the EAP structure is in the second position, where thefirst electrical resistance is different from the second electricalresistance.

In some embodiments, the output based on the electrical resistancecharacteristic of the CPI may correspond to or include the output signal417 generated by the read circuitry 408 as depicted in FIG. 4. Acircuitry (not shown) coupled to the output line 416 may receive theoutput signal 417 and perform an action based on the output signal 417.For example, the circuit coupled the output line 416 may include or haveaccess to a lookup table or another data structure that indicates anaction to be performed based on the output signal 417.

At operation 512, the control circuitry may monitor the output todetermine whether the switch is in the target state. For example, thecontrol circuitry may compare the output signal to an expected outputsignal to determine a resistance of the CPI. If the control circuitrydetermines that the switch is not in the target state, it may adjust thevoltage applied to the EAP structure at operation 514. Additionally, oralternatively, the control circuitry may raise a flag or alert inresponse to determining that the switch is not in the target state. Thealert may be visual (e.g., a light or other indicator), auditory, ortextual. In some embodiments, the alert may be sent to an application(as opposed to a user). For example, if an application is using the CPIas a variable resistor and is controlling the resistance of the CPI, theapplication may be alerted in response to the CPI being in a wrongstate. If the control circuitry determines that the switch is in thetarget state, the method 500 may end.

Turning now to FIG. 6, shown is a high-level block diagram of an examplecomputer system 601 that may be used in implementing one or more of themethods, tools, and modules, and any related functions, described herein(e.g., using one or more processor circuits or computer processors ofthe computer), in accordance with embodiments of the present disclosure.In some embodiments, the major components of the computer system 601 maycomprise one or more CPUs 602, a memory subsystem 604, a terminalinterface 612, a storage interface 616, an I/O (Input/Output) deviceinterface 614, and a network interface 618, all of which may becommunicatively coupled, directly or indirectly, for inter-componentcommunication via a memory bus 603, an I/O bus 608, and an I/O businterface unit 610.

The computer system 601 may contain one or more general-purposeprogrammable central processing units (CPUs) 602A, 602B, 602C, and 602D,herein generically referred to as the CPU 602. In some embodiments, thecomputer system 601 may contain multiple processors typical of arelatively large system; however, in other embodiments the computersystem 601 may alternatively be a single CPU system. Each CPU 602 mayexecute instructions stored in the memory subsystem 604 and may includeone or more levels of on-board cache.

System memory 604 may include computer system readable media in the formof volatile memory, such as random access memory (RAM) 622 or cachememory 624. Computer system 601 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, storage system 626 can be provided forreading from and writing to a non-removable, non-volatile magneticmedia, such as a “hard drive.” Although not shown, a magnetic disk drivefor reading from and writing to a removable, non-volatile magnetic disk(e.g., a “floppy disk”), or an optical disk drive for reading from orwriting to a removable, non-volatile optical disc such as a CD-ROM,DVD-ROM or other optical media can be provided. In addition, memory 604can include flash memory, e.g., a flash memory stick drive or a flashdrive, an SD card, and/or a tape drive (reel/cassette). Memory devicescan be connected to memory bus 603 by one or more data media interfaces.The memory 604 may include at least one program product having a set(e.g., at least one) of program modules that are configured to carry outthe functions of various embodiments.

One or more programs/utilities 628, each having at least one set ofprogram modules 630 may be stored in memory 604. The programs/utilities628 may include a hypervisor (also referred to as a virtual machinemonitor), one or more operating systems, one or more applicationprograms, other program modules, and program data. Each of the operatingsystems, one or more application programs, other program modules, andprogram data or some combination thereof, may include an implementationof a networking environment. Program modules 630 generally perform thefunctions or methodologies of various embodiments.

Although the memory bus 603 is shown in FIG. 6 as a single bus structureproviding a direct communication path among the CPUs 602, the memorysubsystem 604, and the I/O bus interface 610, the memory bus 603 may, insome embodiments, include multiple different buses or communicationpaths, which may be arranged in any of various forms, such aspoint-to-point links in hierarchical, star or web configurations,multiple hierarchical buses, parallel and redundant paths, or any otherappropriate type of configuration. Furthermore, while the I/O businterface 610 and the I/O bus 608 are shown as single respective units,the computer system 601 may, in some embodiments, contain multiple I/Obus interface units 610, multiple I/O buses 608, or both. Further, whilemultiple I/O interface units are shown, which separate the I/O bus 608from various communications paths running to the various I/O devices, inother embodiments some or all of the I/O devices may be connecteddirectly to one or more system I/O buses.

In some embodiments, the computer system 601 may be a multi-usermainframe computer system, a single-user system, or a server computer orsimilar device that has little or no direct user interface, but receivesrequests from other computer systems (clients). Further, in someembodiments, the computer system 601 may be implemented as a desktopcomputer, portable computer, laptop or notebook computer, tabletcomputer, pocket computer, telephone, smart phone, network switches orrouters, or any other appropriate type of electronic device.

It is noted that FIG. 6 is intended to depict the representative majorcomponents of an exemplary computer system 601. In some embodiments,however, individual components may have greater or lesser complexitythan as represented in FIG. 6, components other than or in addition tothose shown in FIG. 6 may be present, and the number, type, andconfiguration of such components may vary.

In addition to embodiments described above, other embodiments havingfewer operational steps, more operational steps, or differentoperational steps are contemplated. Also, some embodiments may performsome or all of the above operational steps in a different order. Themodules are listed and described illustratively according to anembodiment and are not meant to indicate necessity of a particularmodule or exclusivity of other potential modules (or functions/purposesas applied to a specific module).

In the foregoing, reference is made to various embodiments. It should beunderstood, however, that this disclosure is not limited to thespecifically described embodiments. Instead, any combination of thedescribed features and elements, whether related to differentembodiments or not, is contemplated to implement and practice thisdisclosure. Many modifications and variations may be apparent to thoseof ordinary skill in the art without departing from the scope and spiritof the described embodiments. Furthermore, although embodiments of thisdisclosure may achieve advantages over other possible solutions or overthe prior art, whether or not a particular advantage is achieved by agiven embodiment is not limiting of this disclosure. Thus, the describedaspects, features, embodiments, and advantages are merely illustrativeand are not considered elements or limitations of the appended claimsexcept where explicitly recited in a claim(s).

As discussed in more detail herein, it is contemplated that some or allof the operations of some of the embodiments of methods described hereinmay be performed in alternative orders or may not be performed at all;furthermore, multiple operations may occur at the same time or as aninternal part of a larger process.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers, and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the variousembodiments. As used herein, the singular forms “a,” “an,” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“includes” and/or “including,” when used in this specification, specifythe presence of the stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof. In the previous detaileddescription of example embodiments of the various embodiments, referencewas made to the accompanying drawings (where like numbers represent likeelements), which form a part hereof, and in which is shown by way ofillustration specific example embodiments in which the variousembodiments may be practiced. These embodiments were described insufficient detail to enable those skilled in the art to practice theembodiments, but other embodiments may be used and logical, mechanical,electrical, and other changes may be made without departing from thescope of the various embodiments. In the previous description, numerousspecific details were set forth to provide a thorough understanding thevarious embodiments. But, the various embodiments may be practicedwithout these specific details. In other instances, well-known circuits,structures, and techniques have not been shown in detail in order not toobscure embodiments.

Different instances of the word “embodiment” as used within thisspecification do not necessarily refer to the same embodiment, but theymay. Any data and data structures illustrated or described herein areexamples only, and in other embodiments, different amounts of data,types of data, fields, numbers and types of fields, field names, numbersand types of rows, records, entries, or organizations of data may beused. In addition, any data may be combined with logic, so that aseparate data structure may not be necessary. The previous detaileddescription is, therefore, not to be taken in a limiting sense.

The descriptions of the various embodiments of the present disclosurehave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

Although the present invention has been described in terms of specificembodiments, it is anticipated that alterations and modification thereofwill become apparent to those skilled in the art. Therefore, it isintended that the following claims be interpreted as covering all suchalterations and modifications as fall within the true spirit and scopeof the invention.

What is claimed is:
 1. An apparatus comprising: a conductive particleinterconnect (CPI) that includes an elastomeric carrier and a pluralityof conductive particles dispersed therein; and an electroactive polymer(EAP) structure disposed around at least a portion of the CPI, whereinthe EAP is configured to move between a first position and a secondposition in response to an electrical field, wherein the CPI isconfigured to exhibit a first electrical resistance when the EAPstructure is in the first position and to exhibit a second electricalresistance when the EAP structure is in the second position, the secondelectrical resistance being different than the first electricalresistance.
 2. The apparatus of claim 1, wherein the EAP structureapplies a first force to the CPI when the EAP structure is in the firstposition and applies a second force to the CPI when the EAP structure isin the second position, and wherein a magnitude of the first force isdifferent from a magnitude of the second force.
 3. The apparatus ofclaim 2, wherein the magnitudes of the first and second forces aredependent on a magnitude of the electrical field.
 4. The apparatus ofclaim 1, wherein the EAP structure applies a first force to the CPI whenthe EAP structure is in the first position and applies a second force tothe CPI when the EAP structure is in the second position, and wherein adirection of the first force is different from a direction of the secondforce.
 5. The apparatus of claim 1, wherein the EAP structure applies acompressive force to the CPI when the EAP structure is in the secondposition.
 6. The apparatus of claim 1, wherein the EAP structurecompresses the CPI by a first amount when the EAP structure is in thefirst position and compresses the CPI by a second amount when the EAPstructure is in the second position, and wherein the first amount isdifferent from the second amount.
 7. The apparatus of claim 1, whereinthe EAP structure includes a first electrode, a second electrode, and anEAP disposed between the first electrode and the second electrode, andwherein the first and second electrodes are configured to apply avoltage to the EAP to generate the electrical field in response toreceiving a control signal.
 8. The apparatus of claim 1, wherein theconcentration of conductive particles in the CPI is below a percolationlimit such that the CPI is not electrically conductive when the EAP isin the first position.
 9. The apparatus of claim 8, wherein: the CPIacts as an open switch when the EAP structure is in the first position,and the CPI acts as a closed switch when the EAP structure is in thesecond position.
 10. The apparatus of claim 1, the apparatus furthercomprising: control circuitry configured to generate an input signal inresponse to identifying a target state of the CPI; and a voltage sourceconfigured to receive the input signal and generate the electricalfield.
 11. A method comprising: determining a target state of aconductive particle interconnect (CPI); generating an input signal basedon the target state; and transmitting the input signal to a voltagesource to cause an electroactive polymer (EAP) disposed around the CPIto apply a force on the CPI, causing the CPI to transition to the targetstate.
 12. The method of claim 11, the method further comprising:determining a target voltage associated with the target state, whereinthe target voltage is a voltage that causes the EAP to move to a firstposition associated with the target state; and applying, by the voltagesource, the target voltage to the EAP.
 13. The method of claim 11, themethod further comprising: monitoring, after transmitting the inputsignal to the voltage source, an output of the CPI; and determining,based on the monitoring, whether the CPI is in the target state.
 14. Themethod of claim 13, wherein monitoring the output of the CPI includesdetermining a resistance of the CPI, the method further comprising:adjusting, in response to determining that the CPI is not in the targetstate, a voltage applied to the EAP, wherein the adjusting includes: inresponse to the resistance of the CPI being too high, increasing thevoltage applied to the EAP to cause further compression of the CPI; andin response to the resistance of the CPI being too low, decreasing thevoltage applied to the EAP to reduce compression of the CPI.
 15. Themethod of claim 11, wherein: the CPI is configured to act as a switchhaving two or more states, each of the two or more states havingassociated position of the EAP; and transmitting the input signal to thevoltage source causes the EAP to move into a position associated withthe target state.
 16. A computer program product comprising a computerreadable storage medium having program instructions embodied therewith,the program instructions executable by processor to cause the processorto perform a method comprising: determining a target state of aconductive particle interconnect (CPI); generating an input signal basedon the target state; and transmitting the input signal to a voltagesource to cause an electroactive polymer (EAP) disposed around the CPIto apply a force on the CPI, causing the CPI to transition to the targetstate.
 17. The computer program product of claim 16, wherein the methodfurther comprises: determining a target voltage associated with thetarget state, wherein the target voltage is a voltage that causes theEAP to move to a first position associated with the target state; andapplying, by the voltage source, the target voltage to the EAP.
 18. Thecomputer program product of claim 16, wherein the method furthercomprises: monitoring, after transmitting the input signal to thevoltage source, an output of the CPI; and determining, based on themonitoring, whether the CPI is in the target state.
 19. The computerprogram product of claim 18, wherein monitoring the output of the CPIincludes determining a resistance of the CPI, the method furthercomprising: adjusting, in response to determining that the CPI is not inthe target state, a voltage applied to the EAP, wherein the adjustingincludes: in response to the resistance of the CPI being too high,increasing the voltage applied to the EAP to cause further compressionof the CPI; and in response to the resistance of the CPI being too low,decreasing the voltage applied to the EAP to reduce compression of theCPI.
 20. The computer program product of claim 16, wherein: the CPI isconfigured to act as a switch having two or more states, each of the twoor more states having associated position of the EAP; and transmittingthe input signal to the voltage source causes the EAP to move into aposition associated with the target state.